Quantifying Resilience from Individual Feed Intake Data in a Natural Disease Challenge Model for Growing Pigs

Quantifying resilience in a health challenged environment could be beneficial to add information in commercial crossbred testing systems beyond mortality. Mortality and treatment records can be biased due to the subjective nature of euthanizing or treating individuals. Mortality may also capture other problems (e.g. ruptures) that are not linked to disease resilience. Objective measures would help quantify resilience to disease and other stressors. Feed intake is sensitive to disease due to the physiological effects of illness on feed intake. To study resilience, a natural challenge model was set up in Quebec, Canada. Every three weeks, batches of ~60-75 F₁ (Large White x Landrace) healthy weaned barrows were sent to a high health quarantine nursery to take pre-challenge samples for potential predictors of resilience and then sent to the challenge facility after ~3 weeks. From the first 1341 animals, two separate measures of resilience were calculated using individual daily feed intake. The first involved regressing daily feed intake (FI) or duration at the feeder (DUR) on age and extracting the root mean square error (RMSE) within individual (RMSE_FI and RMSE_DUR, respectively). The second measure was computed as the percentage of negative residuals for an animal from quantile regression of FI on age using the 0.05 quantile across animals (FIQR₀₅), which were classified as sick days. Mortality (0/1) and treatment rate per day times 180 days (TRT180) were used to validate the resilience measures. Heritability estimates for RMSE_FI, RMSE_DUR, and FIQR₀₅ were 0.22 (±0.07), 0.25 (±0.08), and 0.17 (±0.06), respectively. Heritability estimates for mortality and TRT180 were 0.13 (0.05) and 0.29 (0.07). The genetic correlation between mortality and TRT180 was 0.93 (±0.14). RMSE_FI and RMSE_DUR had a genetic correlation with mortality of 0.54 (±0.36) and 0.65 (±0.35), respectively. RMSE_FI and RMSE_DUR had genetic correlations with TRT180 of 0.56 (±0.20) and 0.64 (±0.14), respectively. FIQR₀₅ showed positive genetic correlations of 0.40 (±0.40) and 0.87 (±0.10) with mortality and TRT180, respectively. FIQR₀₅ also showed moderate to strong negative genetic correlations of -0.70 (±0.18) and -0.76 (±0.19) with finishing average daily gain (ADG) and average daily feed intake (ADFI). RMSE measures showed lower genetic correlations with ADG and ADFI (-0.31±0.27 and -0.19±0.26 for RMSE_FI and RMSE_DUR, respectively). This research demonstrates that resilience measures that are genetically correlated with mortality and treatment rate can be extracted from feed intake data. Funding from Genome Alberta (ALGP2), Genome Canada, and PigGen Canada.